断陷盆地基底及周缘性质对盆缘构造和沉积的影响与制约——以伊通地堑为例

THE INFLUENCE AND CONTROL OF THE BASEMENT AND PERIPHERY OF FAULT BASIN TO THE STRUCTURE AND DEPOSITION OF BASIN MARGIN:A case study of Yitong graben

伊通地堑基底主要由抗风化能力强、刚性的块状花岗岩系和抗风化能力弱、相对柔弱的层状沉积岩系组成.东南边界断层受基底岩性影响明显,花岗岩系构成的区段内表现为断面平直的高角度张性断裂活动样式,层状岩系区段内为典型的铲状正断层.西北缘边界断裂构造活动样式基本不受基底岩性影响.基底岩性的差异很大程度上影响和制约边缘沉积相带组合类型、发育规模、展布规律.花岗岩系区段内,西北缘沉积体系由深湖相夹水下扇的特殊类型——跌水扇相构成,东南缘沉积体系由小型扇三角洲和滨浅湖相构成.层状岩系区段内,沉积体系主要由辫状三角洲相和滨浅湖相构成.

The basement of Yitong graben is composed of granite and stratified sedimentary series. The boundary faults in the southeastern margin of the graben are obviously affected by the basement lithology. In the granite area, high angle extensional faults are developed. While in the sedimentary rock area, listric faults are developed. The style of boundary faults in the northwestern margin is rarely affected by the basement lithology. The assemblage, size and distribution of sedimentary facies in the basin margin are mostly influenced and controlled by different basement lithology. In the area with granite basement, the depositional system of northwestern margin consists of deep lake facies and a special subaqueous fan -- waterfall fan -- facies. While the depositional system of southeastern margin is mainly small fan-delta and shore-shallow lacustrine facies. In the area with stratified rock basement, the sedimentary system is mainly composed of braided delta and shore-shallow lacustrine facies.